feat(package): add --preserve-output flag

.changeset/mean-ladybugs-sparkle.md

@@ -0,0 +1,5 @@
+---
+"@sveltejs/package": minor
+---
+
+feat: add `--preserve-output` flag to prevent deletion of the output directory before packaging

documentation/docs/30-advanced/70-packaging.md

@@ -242,6 +242,7 @@ You can create so-called declaration maps (`d.ts.map` files) by setting `"declar
 - `-w`/`--watch` — watch files in `src/lib` for changes and rebuild the package
 - `-i`/`--input` — the input directory which contains all the files of the package. Defaults to `src/lib`
 - `-o`/`--output` — the output directory where the processed files are written to. Your `package.json`'s `exports` should point to files inside there, and the `files` array should include that folder. Defaults to `dist`
+- `-p`/`--preserve-output` — prevent deletion of the output directory before packaging. Defaults to `false`, which means that the output directory will be emptied first
 - `-t`/`--types` — whether or not to create type definitions (`d.ts` files). We strongly recommend doing this as it fosters ecosystem library quality. Defaults to `true`
 - `--tsconfig` - the path to a tsconfig or jsconfig. When not provided, searches for the next upper tsconfig/jsconfig in the workspace path.
 

packages/package/src/cli.js

@@ -23,6 +23,7 @@ prog
 	.describe('Create a package')
 	.option('-i, --input', 'Input directory')
 	.option('-o, --output', 'Output directory', 'dist')
+	.option('-p, --preserve-output', 'Do not delete the output directory before packaging', false)
 	.option('-t, --types', 'Emit type declarations', true)
 	.option('-w, --watch', 'Rerun when files change', false)
 	.option(
@@ -47,6 +48,7 @@ prog
 				cwd: process.cwd(),
 				input: args.input ?? config.kit?.files?.lib ?? 'src/lib',
 				output: args.output,
+				preserve_output: args['preserve-output'],
 				tsconfig: args.tsconfig,
 				types: args.types,
 				config

packages/package/src/index.js

@@ -41,7 +41,10 @@ async function do_build(options, analyse_code) {
 		await process_file(input, temp, file, options.config.preprocess, alias, tsconfig, analyse_code);
 	}
 
-	rimraf(output);
+	if (!options.preserve_output) {
+		rimraf(output);
+	}
+
 	mkdirp(output);
 	copy(temp, output);
 
@@ -173,6 +176,7 @@ export async function watch(options) {
 function normalize_options(options) {
 	const input = path.resolve(options.cwd, options.input);
 	const output = path.resolve(options.cwd, options.output);
+	const preserve_output = options.preserve_output;
 	const temp = path.resolve(
 		options.cwd,
 		options.config.kit?.outDir ?? '.svelte-kit',
@@ -189,6 +193,7 @@ function normalize_options(options) {
 	return {
 		input,
 		output,
+		preserve_output,
 		temp,
 		extensions,
 		alias,

packages/package/src/types.d.ts

@@ -4,6 +4,7 @@ export interface Options {
 	cwd: string;
 	input: string;
 	output: string;
+	preserve_output: boolean;
 	types: boolean;
 	tsconfig?: string;
 	config: {

packages/package/test/fixtures/preserve-output/expected/assets/theme.css

@@ -0,0 +1 @@
+:root { color: red }

packages/package/test/fixtures/preserve-output/expected/index.d.ts

@@ -0,0 +1 @@
+export declare const foo = 'bar';

packages/package/test/fixtures/preserve-output/expected/index.js

@@ -0,0 +1 @@
+export const foo = 'bar';

packages/package/test/fixtures/preserve-output/package.json

@@ -0,0 +1,16 @@
+{
+	"name": "preserve-output",
+	"private": true,
+	"type": "module",
+	"description": "with additional things running before svelte-package",
+	"peerDependencies": {
+		"svelte": "^4.0.0"
+	},
+	"exports": {
+		".": {
+			"types": "./dist/index.d.ts",
+			"svelte": "./dist/index.js"
+		},
+		"./theme.css": "./dist/assets/theme.css"
+	}
+}

packages/package/test/fixtures/preserve-output/src/lib/index.ts

@@ -0,0 +1 @@
+export const foo = 'bar';

packages/package/test/fixtures/preserve-output/tsconfig.json

@@ -0,0 +1,5 @@
+{
+	"compilerOptions": {
+		"target": "ESNext"
+	}
+}

packages/package/test/index.spec.js

@@ -31,6 +31,7 @@ async function test_make_package(path, options) {
 		cwd,
 		input,
 		output,
+		preserve_output: false,
 		types: true,
 		config,
 		...options
@@ -93,7 +94,7 @@ for (const dir of fs.readdirSync(join(__dirname, 'errors'))) {
 		const input = resolve(cwd, config.kit?.files?.lib ?? 'src/lib');
 
 		try {
-			await build({ cwd, input, output, types: true, config });
+			await build({ cwd, input, output, types: true, config, preserve_output: false });
 			throw new Error('Must not pass build');
 		} catch (/** @type {any} */ error) {
 			expect(error).toBeInstanceOf(Error);
@@ -183,6 +184,7 @@ if (!process.env.CI) {
 			cwd,
 			input: 'src/lib',
 			output: 'package',
+			preserve_output: false,
 			types: true,
 			config
 		});
@@ -271,6 +273,7 @@ test('validates package (1)', () => {
 		cwd: '',
 		input: '',
 		output: '',
+		preserve_output: false,
 		types: true
 	});
 	analyse_code('src/lib/index.js', 'export const a = 1;import.meta.env;');
@@ -290,6 +293,7 @@ test('validates package (2)', () => {
 		cwd: '',
 		input: '',
 		output: '',
+		preserve_output: false,
 		types: true
 	});
 	analyse_code('src/lib/C.svelte', '');
@@ -309,6 +313,7 @@ test('validates package (all ok 1)', () => {
 		cwd: '',
 		input: '',
 		output: '',
+		preserve_output: false,
 		types: true
 	});
 	analyse_code('src/lib/C.svelte', '');
@@ -326,6 +331,7 @@ test('validates package (all ok 2)', () => {
 		cwd: '',
 		input: '',
 		output: '',
+		preserve_output: false,
 		types: true
 	});
 	analyse_code('src/lib/C.svelte', '');
@@ -337,3 +343,11 @@ test('validates package (all ok 2)', () => {
 
 	expect(warnings.length).toEqual(0);
 });
+
+test('create package with preserved output', async () => {
+	const output = join(__dirname, 'fixtures', 'preserve-output', 'dist');
+	rimraf(output);
+	fs.mkdirSync(join(output, 'assets'), { recursive: true });
+	fs.writeFileSync(join(output, 'assets', 'theme.css'), ':root { color: red }');
+	await test_make_package('preserve-output', { preserve_output: true });
+});